Unvaccinated behind largest U.S. measles outbreak in years

The largest U.S. outbreak of measles to occur in 15 years -- affecting 214 children so far -- is likely driven by travelers returning from abroad and by too many unvaccinated U.S. children, according to new research.

The finding could highlight the dangers of a trend among some U.S. parents to skip the measles-mumps-rubella (MMR) vaccine for their children, out of what many experts call misguided fears over its safety.

Dr. Andrew Pavia, professor of pediatrics at the University of Utah and spokesman for the Infectious Diseases Society of America (IDSA), said, "The good news is that we are seeing introductions of measles that are being contained as small outbreaks."

Pavia credits containment to high levels of vaccination and thevacci rapid response by public health officials. However, if an outbreak occurred in a "really susceptible population the outcome could be very different," he said.

"What would happen in an area with a lot of vaccine refusers? Then you might see a much larger outbreak," he said.

Several measles-related studies were unveiled at the annual IDSA annual meeting, currently being held in Boston.